The present invention relates generally to a setting gripper for an anchor device of the type comprising two co-axial components of which each has a head and of which the heads are mutually spread co-axially during setting.
The discussion that follows, both with regard to prior art setting grippers and the setting gripper of the present invention, describe the construction of several components of the setting grippers, as well as the operation of the setting grippers, with references to various zones of mutual contact between various components. As such, the term xe2x80x9czonexe2x80x9d is used herein to refer to an area of a particular component on which contact with an associated component is possible. In this regard, the two mutually contacting components are akin to a hypothetical cam and a hypothetical cam follower wherein the cam is movable relative to a cam follower over a predetermined area of the surface of the cam follower. The portion of the surface of the cam that is capable of contacting the surface of the cam follower would be collectively referred to as the xe2x80x9czone on the camxe2x80x9d while the portion of the surface of the cam follower that is capable of contacting the surface of the cam would be collectively referred to as the xe2x80x9czone on the cam followerxe2x80x9d. The zone of the cam and the zone of the cam follower collectively represent a zone of mutual contact between the cam and the cam follower.
The discussion herein is somewhat more complex, as the exemplary setting gripper of the present invention includes two pair of contacting components that have a common component. The exemplary setting gripper 16 illustrated in FIG. 3 includes a lever 20 that is movably coupled to both a gripper body 19 (via a shank 113) and a slider 21 (via a pin 110). When the term xe2x80x9czonexe2x80x9d is used herein with reference to the gripper body 19, it designates an area on the gripper body 19 that is capable of contacting a corresponding area on the lever 20, such as zones 81 and 84 on the gripper body 19 which are capable of contacting zone 106 on the lever 20, or the bottom 93 and top 94 of the apertures 88 (i.e., zones 93 and 94) and the shank 113 (i.e., zone 113). Similarly, when the term xe2x80x9czonexe2x80x9d is used herein with reference to the slider 21, it designates an area on the slider 21 that is capable of contacting a corresponding area on the lever 20, such as notch 64 (i.e., zone 64) and pin 110 (i.e., zone 110). When the term xe2x80x9czonexe2x80x9d is used herein with reference to the lever 20, it designates an area on the lever 20 that is capable of contacting a corresponding area (or zone) on the other specified component (i.e., the one of the gripper body 19 and the slider 21 that is specifically mentioned). The corresponding zones of gripper body 19 and the lever 20 represent a zone of mutual contact between the gripper body 19 and the lever 20 whereas the corresponding zones of the slider 21 and the lever 20 represent a zone of mutual contact between the slider 21 and the lever 20.
Setting grippers for co-axial expanding wall anchors typically include:
a gripper body having an integral handle and a flat jaw perpendicular to a predetermined direction of the body;
a slider having an integral flat jaw perpendicular to said predetermined direction and placed opposite the jaw of the gripper body in said predetermined direction, the slider being guided so as to translate in said predetermined direction relative to the gripper body in the sense of moving away from the jaw of the slider relative to the jaw of the gripper body, from a relative rest position in which the two jaws are mutually adjacent and capable of being inserted together between the heads of the two components prior to setting, then in the opposite direction as they return;
a lever positioned and supported by a respectively corresponding zone in said predetermined direction against a zone of the slider and in the opposite direction against a zone of the gripper body offset in relation to said zone of the slider perpendicularly to said predetermined direction, and pivot axes perpendicular to a plane containing said predetermined direction, the lever having an integral handle and said lever and gripper body handles being disposed relative to one another and relative to said zones so as to allow the two handles to be gripped by one hand by the user in such a way that squeezing the handles together from a relative rest position moves the slider in said predetermined direction relative to the gripper body;
a holding arrangement for fixing the position of a zone of the lever perpendicular to said predetermined direction in said plane relative to the gripper body and/or to the slider; and
a spring or other arrangement for returning the handles of the slider, on the one hand, and of the gripper body, on the other hand, to their respective relative rest positions.
As non-limiting examples of anchoring devices of the type concerned, expanding metal plugs of which an embodiment is described in French patent 2,546,989 and sold under the registered trade mark xe2x80x9cMollyxe2x80x9d and which is set when a screw is engaged coaxially therein by pulling on the head of the screw while holding the plug by a flange integral therewith and forming a head for supporting it on a hollow support in a hole of which setting is effected. Certain rivets which are set blind are also known and, in general, any anchoring device which is set blind by co-axial spreading apart of heads of components which are themselves co-axial (whatever the configuration of these heads and the nature of these components) are considered to be similar to such expanding metal plugs.
Various embodiments of grippers for the setting of such anchoring devices have been proposed, the most highly developed and the most satisfactory hitherto being described in British patent application 2,289,006, which describes a gripper of the type mentioned above in which a lever is supported on a gripper body via a pivot which is stationary relative to the lever and the body. Such an arrangement only allows a relative rotational movement about the corresponding axis, whereas the lever is also supported on a slider between this axis and the handles by way of a cam portion of the lever and an opposing part of the slider. As the handles are brought together by clenching of the user""s fist, the zone of mutual support for the lever and the slider gradually moves away from the axis of articulation of the lever on the gripper body.
Thus, in an initial phase of setting of the anchor device, in particular an expanding metal plug, that is in a phase which is generally found to require a much greater force than the following phases to bring about the spreading apart of the heads of the two components (namely the screw head and the plug head in this example) the minimum value of the lever arm between the zone of mutual contact between the lever and the slider and the axis of articulation of the lever on the gripper body allows the user to apply to the heads a maximum spreading force by means of a more reasonable force applied to squeeze the handles together. This lever arm then increases progressively as the handles are brought together and as the two heads are spread apart, which means that less force is required for this purpose. When setting an expanding metal plug, in particular, it is particularly important that, after setting, the application of such a squeezing force on the handles does not risk causing the screw to tear away from the plug. The tapping in the plug, and the known gripper described in British patent application 2 289 006 is able to reconcile the need to apply a considerable force in spreading apart the heads of the screw and the plug in the initial phase of setting or starting phase of expansion, and the need to limit this force at the end of setting.
This development is more satisfactory than previously grippers, it also offers great simplicity in production and use and provides an improved guidance of the slider inside the gripper body, preventing misalignment of these two components of the anchoring device during the setting operation. However, this known gripper has a considerable number of drawbacks.
One of these drawbacks resides in the considerable frictional forces which build up between the lever cam and the counterpart of the slider as the handles are brought together, and as the anchor device is set. These forces obviously increase the force to be applied to the handles for a given resistance of the two components to the spreading apart of the heads. In particular, if a gripper of this type can be used for setting expanding metal plugs intended to cooperate with screws having a diameter of up to 6 mm, the setting of the plugs intended for larger diameter screws by means of such grippers would necessitate a force on the handles that is generally beyond the scope of an average setting tool. Furthermore, this friction causes rapid wear of the cam and/or of its counterpart on the slider.
Finally, in such a device, as the zone of mutual contact between the lever cam and its counterpart on the slider progressively moves away from the axis of articulation of the lever on the gripper body, the forces applied by the lever cam to the counterpart on the slider are necessarily markedly offset relative to the common axis of the two components of the anchor device during the majority of setting operation. This tends to move the slider out of true alignment relative to the gripper body and therefore applies additional resistance to the movement of the handles toward each other due to friction in this region.
It is the object of the present invention to overcome these drawbacks and others. The present invention preferably provides a gripper of the general type mentioned above, characterized in that it comprises a plurality of such zones of the gripper body and corresponding zones of the lever, at different distances from such zone of the slider and from the corresponding zone of the lever perpendicular to such predetermined direction on the same side of the zone of the slider and of the corresponding zone of the lever and distributed in such predetermined direction and perpendicular thereto such that the lever pivots relative to the gripper body about axes at increasing distances from said zone of the slider and from the corresponding zone of the lever in succession as the handles are squeezed together, each of said plurality of said zone of the gripper body allowing for movement of the corresponding zone of the lever, at least in said predetermined direction.
A preferred gripper according to the invention therefore retains the advantageous characteristic of increasing the lever arm as the handles are brought together as setting proceeds in a manner which is particularly well adapted to the setting of expanding metal plugs. This progression is obviously discontinuous, whereas it is continuous in the case of a gripper according to the teachings of the aforementioned British patent application owing to the cooperation between the lever cam and the counterpart on the slider. Experience has shown that such a discontinuity is quite acceptable if there is an adequate number of cooperating zones of the body and the lever and if their distribution (in the sense of moving away from the cooperating zones of the slider and the lever) is selected appropriately. In the case of a gripper intended for the setting of expanding metal plugs, three of such cooperating zones of the gripper body and of the lever are usually considered sufficient, but a different number could be selected without departing from the scope of the present invention.
Also, the method of cooperation according to the present invention between the lever, on the one hand, and the gripper body and the slider, on the other hand, has significant advantages over the method of cooperation recommended in the aforementioned British patent application. In fact, the range of variation of the lever arm may be much greater as it can be distributed over the entire size of the lever between its zone cooperating with the slider and the handle of the lever and in a corresponding manner on the gripper body whereas the size of the cam and of its counterpart on the slider, perpendicularly to the direction of sliding thereof, in the case of a gripper according to the aforementioned British patent application is necessarily much more limited, in particular on account of the design of the slider and its cooperation with the gripper body.
Furthermore, the friction occurring, in a gripper according to the invention, between the cooperating zones of the lever and the gripper body apply much lower resistance to squeezing the handles together than that occurring between the lever cam and its counterpart on the slider in the case of a gripper according to the aforementioned British patent application. Thus, the performance of a gripper according to the invention is improved over that of a gripper according to the aforementioned British patent application in terms of spreading force applied to the heads of the two components of the anchor device relative to the force applied to squeeze the handles together.
In addition, the position of the cooperating zones of the slider and of the lever perpendicular to the direction of translation of the slider varies far less in the case of a gripper according to the invention than in the case of a gripper according to the teaching of the aforementioned British patent application, thus making it is possible to keep them sufficiently close to the axis of the two components of the anchor device. This makes the tendency of the slider to rock relative to the gripper body to remain particularly moderate, in fact virtually negligible, so that the friction occurring between the slider and the gripper body is much lower than in the case of a gripper according to the teaching of the aforementioned British patent application. This further increases the performance of the gripper according to the present invention as defined herein before.
The arrangement for holding a zone of the lever relative to the body of the gripper and/or to the slider can be located in cooperating zones of the lever and of the slider, which are mounted so as to rotate relative to one another about an axis which is stationary relative to the lever and relative to the slider which enables this axis to be passed in the immediate vicinity of the common axis of the two components of the anchor device to be set. Thus this favorably enables the force of the lever to be applied to the slider virtually in the axis of these parts. However, this results in the pivoting of the lever relative to the gripper body being accompanied by relative sliding perpendicular to the direction of translation of the slider relative to the gripper body even in the region of the cooperating zones of the lever and of the gripper body closest to the cooperating zones of the slider lever that is even in a configuration in which the forces applied (in particular between the lever and the gripper body) are the highest, and consequently causes similarly high friction.
Consequently, it is preferable to adopt a compromise whereby the holding arrangement or components are located in one of said zones of the gripper body and of the slider and in the corresponding zone of the lever and to adopt a comprise arrangement for mutual immobilisation against any relative translation at least approximately perpendicularly to said predetermined direction, whereas the others of said zones of the gripper body and of the slider and the respectively corresponding zones of the lever allow a relative movement approximately perpendicularly to said direction.
More precisely, it is preferable if said holding arrangement includes, in the zone of said zones of the gripper body closest to said zone of the slider and in the corresponding zone of the lever, arrangement for guidance in relative translation at least approximately in said predetermined direction. Therefore, if the rotation of the lever relative to the gripper body is effected by their cooperating zones closest to the cooperating zones of the lever and the slider that is if the forces between the lever and the gripper body are greatest, their relative movement is virtually exclusively a rotational movement and the losses by friction in this region are reduced to a minimum.
Advantageously, therefore, the other zone, of which there is at least one, of said zones of the gripper body or the corresponding zone of the lever comprises a convex surface in the form of part of a cylinder of revolution about the corresponding axis, for the support of this zone of the lever on this zone of the gripper body in the direction opposed to said predetermined direction. This is a particularly simple method of allowing the necessary rotation, the clearance required to substitute one axis for another during the pivoting of the lever relative to the gripper body, and a relative translation perpendicularly to the direction of translation of the slider relative to the gripper body in their cooperating zones.
Furthermore, the zone of the slider and said corresponding zone of the lever are preferably designed in such a way that they provide for guidance in relative translation at least approximately perpendicular to said predetermined direction in order to maintain of relative deflection in this direction also at this level.
It might be observed that the relative translation movements in the region of the cooperating zones of the slider and of the lever and of the cooperating zones of the gripper body and of the lever apart from those in which the holding arrangement or components are located are necessarily accompanied by friction which affects the performance of the gripper as defined above. However, it will also be observed that this friction is manifested essentially after the starting phase of setting which is carried out by pivoting the lever over the gripper body by its zones processed to the cooperating zones of the zone of the slider and the corresponding zone of the lever in the preferred position of the holding means which ensure pure relative rotation, on the one hand. It will also be observed that the aforementioned preferred configuration of the other cooperating zones of the lever and of the gripper body as well as of the lever and the slider allow the relative travel subjected to friction to be reduced considerably in comparison with the case of a gripper according to the teaching of the aforementioned British patent application, to the extent that the gripper according to the invention has both better performance and greater convenience in use.
If, as preferred, the cooperating zones of the slider and of the lever include an arrangement for guidance in relative translation at least approximately perpendicular to the direction of translation of the slider relative to the gripper body, elastic components for returning the handles in a spreading direction toward their relative rest position, according to a preferred embodiment of the gripper according to the invention, also ensure that the slider and the gripper body are returned to their relative rest position.
The configuration of the gripper according to the invention should be adapted to the configuration of the anchor devices which it is intended to set, this being the case, in particular, with the configuration of its jaws. For example, if the gripper is intended to set expanding metal plugs or other anchor devices of which one of the components include a shank integrally carrying its head and issuing from the other component in the region of its head, the two jaws advantageously have, in a same plane including said predetermined direction and constituting a mean plane of symmetry common to the slider and to the gripper body, a respective notch for engagement on one of the two components which comprises the shank, the two notches being open on either side in said direction and in a direction perpendicular thereto to allow the shank to pass between the two heads.
For ease of maintenance or else to allow adaptation of one gripper to different anchor devices, such as to satisfy a wide range of dimensions and/or configurations of the components of these anchor devices, the two jaws are preferably interchangeable. This can be provided by way of the inter-changeability of the entire slider with regard to its jaw and by way of the fact that the gripper body includes an interchangeable nose constituting the corresponding jaw. For the same purpose, the cooperation between at least one of the jaws and the corresponding component of the anchor device is achieved by way of an appropriately configured adaptor attached integrally but removably, for example by magnetic fixing, to this jaw.
Further characteristics and advantages of a gripper according to the invention will emerge from the following description relating to a non-limiting exemplary embodiment but corresponding to the currently preferred embodiment, and from the accompanying drawings and claims which form an integral part of this description.